# Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
#
# This source code is licensed under the BSD license found in the
# LICENSE file in the root directory of this source tree.

import dataclasses
import json
import logging
import os
import platform
from typing import Any, Dict, Optional

import torch

logger = logging.getLogger("xformers")

UNAVAILABLE_FEATURES_MSG = (
    "  Memory-efficient attention, SwiGLU, sparse and more won't be available."
)


@dataclasses.dataclass
class _BuildInfo:
    metadata: Dict[str, Any]

    @property
    def cuda_version(self) -> Optional[int]:
        return self.metadata["version"]["cuda"]

    @property
    def torch_version(self) -> str:
        return self.metadata["version"]["torch"]

    @property
    def python_version(self) -> str:
        return self.metadata["version"]["python"]

    @property
    def flash_version(self) -> str:
        return self.metadata["version"].get("flash", "0.0.0")

    @property
    def build_env(self) -> Dict[str, Any]:
        return self.metadata["env"]


class xFormersWasNotBuiltException(Exception):
    def __str__(self) -> str:
        return (
            "Need to compile C++ extensions to use all xFormers features.\n"
            "    Please install xformers properly "
            "(see https://github.com/facebookresearch/xformers#installing-xformers)\n"
            + UNAVAILABLE_FEATURES_MSG
        )


class xFormersInvalidLibException(Exception):
    def __init__(self, build_info: Optional[_BuildInfo]) -> None:
        self.build_info = build_info

    def __str__(self) -> str:
        if self.build_info is None:
            msg = "xFormers was built for a different version of PyTorch or Python."
        else:
            msg = f"""xFormers was built for:
    PyTorch {self.build_info.torch_version} with CUDA {self.build_info.cuda_version} (you have {torch.__version__})
    Python  {self.build_info.python_version} (you have {platform.python_version()})"""
        return (
            "xFormers can't load C++/CUDA extensions. "
            + msg
            + "\n  Please reinstall xformers "
            "(see https://github.com/facebookresearch/xformers#installing-xformers)\n"
            + UNAVAILABLE_FEATURES_MSG
        )


def _register_extensions():
    import importlib
    import os

    import torch

    # load the custom_op_library and register the custom ops
    lib_dir = os.path.dirname(__file__)
    if os.name == "nt":
        # Register the main torchvision library location on the default DLL path
        import ctypes
        import sys

        kernel32 = ctypes.WinDLL("kernel32.dll", use_last_error=True)
        with_load_library_flags = hasattr(kernel32, "AddDllDirectory")
        prev_error_mode = kernel32.SetErrorMode(0x0001)

        if with_load_library_flags:
            kernel32.AddDllDirectory.restype = ctypes.c_void_p

        if sys.version_info >= (3, 8):
            os.add_dll_directory(lib_dir)
        elif with_load_library_flags:
            res = kernel32.AddDllDirectory(lib_dir)
            if res is None:
                err = ctypes.WinError(ctypes.get_last_error())
                err.strerror += f' Error adding "{lib_dir}" to the DLL directories.'
                raise err

        kernel32.SetErrorMode(prev_error_mode)

    loader_details = (
        importlib.machinery.ExtensionFileLoader,
        importlib.machinery.EXTENSION_SUFFIXES,
    )

    extfinder = importlib.machinery.FileFinder(lib_dir, loader_details)
    ext_specs = extfinder.find_spec("_C")
    if ext_specs is None:
        raise xFormersWasNotBuiltException()
    cpp_lib_json = os.path.join(lib_dir, "cpp_lib.json")
    with open(cpp_lib_json, "r") as fp:
        build_metadata = _BuildInfo(json.load(fp))
    try:
        torch.ops.load_library(ext_specs.origin)
    except OSError as exc:
        raise xFormersInvalidLibException(build_metadata) from exc
    return build_metadata


_cpp_library_load_exception = None
_build_metadata: Optional[_BuildInfo] = None

try:
    _build_metadata = _register_extensions()
except (xFormersInvalidLibException, xFormersWasNotBuiltException) as e:
    ENV_VAR_FOR_DETAILS = "XFORMERS_MORE_DETAILS"
    if os.environ.get(ENV_VAR_FOR_DETAILS, False):
        logger.warning(f"WARNING[XFORMERS]: {e}", exc_info=e)
    else:
        logger.warning(
            f"WARNING[XFORMERS]: {e}\n  Set {ENV_VAR_FOR_DETAILS}=1 for more details"
        )
    _cpp_library_load_exception = e

_built_with_cuda = (
    _build_metadata is not None and _build_metadata.cuda_version is not None
)